Hydrogel compositions

ABSTRACT

Fragmented polysaccharide based hydrogel compositions and methods of making and using the same are provided. The subject polysaccharide based hydrogel compositions are prepared by combining a polysaccharide component with a hydrophilic polymer and a cross-linking agent. Also provided are kits and systems for use in preparing the subject compositions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/069,639, filed on Mar.14, 2016, now U.S. Pat. No. 9,592,299which is acontinuation of U.S. patent application Ser. No. 14/339,336, filed onJul. 23, 2014now U.S. Pat. No. 9,289,449which is a continuation of U.S.patent application Ser. No. 13/505,684, filed on Jun. 6, 2012, now U.S.Pat. No. 8,795,727, which is a 371 of International Application SerialNo. PCT/US 2010/055716filed on Nov. 5, 2010, which claims the benefit ofU.S. provisional No. 61/259,566, filed on Nov. 9, 2009, which are hereinincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

Hydrogels are water-swollen networks of hydrophilic homopolymers orcopolymers. These networks may be formed by various techniques; however,the most common synthetic route is the free radical polymerization ofvinyl monomers in the presence of a difunctional cross-linking agent anda swelling agent. The resulting polymer exhibits both liquid-likeproperties, attributable to the major constituent, water, and solid-likeproperties due to the network formed by the cross-linking reaction.These solid-like properties take the form of a shear modulus that isevident upon deformation.

Hydrogels offer biocompatibility and have been shown to have reducedtendency for inducing thrombosis, encrustation and inflammation whenused in medical devices. Unfortunately, the use of hydrogels inbiomedical device applications has been hindered by limitations on theform and mechanical characteristics of the existing hydrogels. Manymedical devices use hydrogels to improve device biocompatibility;however, many hydrogels can only be used in coatings. Many hydrogelssuffer from low modulus, low yield stress, and low strength whencompared to non-swollen polymer systems. Lower mechanical propertiesresult from the swollen nature of hydrogels and the non-stress bearingnature of the swelling agent. Existing in situ cured hydrogels provide abenefit in that they can flow to fit a particular tissue, void, orlumen. However, these materials often lose that ability once they cure,and become subject to the drawbacks listed above. Fully cured hydrogelsare easier to handle, but lack the shape-filling, conformablecharacteristics of the in situ curing systems.

Of particular note is that while the biocompatible and conformablecharacteristics of in situ cured hydrogels are desirable, the methods ofapplying in situ curing hydrogels are cumbersome. The restriction ofkeeping two or more reactive components separate from each other andstable during shipment and storage of devices of this type presents asignificant burden on the user. Typically, the reactive components arestored apart from any reconstituting fluids in the device kits. At thepoint of use, the user is required to assemble multiple containers,reconstitute the materials, and transfer the reconstituted materials toa delivery system prior to applying the material. In some cases thisprocess must be completed within a certain time limit to prevent loss ofactivity of the hydrogel material.

As such, there is a continuing need to develop new compositions capableof forming in situ biocompatible hydrogel structures that offer improvedtherapeutic outcomes.

RELEVANT LITERATURE

U.S. Pat. Nos. 4,963,489; 5,080,655; 5,250,020; 5,266,480; 5,278,201;5,278,204; 5,324,775; 5,443,950; 5,599,916; 5,609,629; 5,618,622;5,652,347; 5,690,955; 5,725,498; 5,741,223; 5,827,937; 5,836,970;5,852,024; 5,874,417; 5,874,500; 6,071,301; 6,344,272; 6,418,934;6,428,811; 6,444,797; 6,530,994; 6,551,610; 6,566,406; 6,602,952;6,645,517; 7,166,574; 7,303,757; 7,414,028; 7,482,427; 7,528,105; and7,670,592.

U.S. Pat. App. Nos. 2006/0241777, 2007/0196454 and 2007/0231366. and.

Foreign Patent Document No. WO 2009/028965.

Braunova et. al. Collect. Czech. Chem. Commun. 2004, 69: 1643-1656.

Carlson, R. P. et. al. Journal of Polymer Science, Polymer Edition.2008, 19(8): 1035-1046.

SUMMARY OF THE INVENTION

Fragmented hydrogel compositions and methods of making and using thesame are provided. The subject hydrogel compositions are prepared bycombining a polymer component and a cross-linking agent followed by afragmentation process to produce a composition of fragmented hydrogel.Also provided are kits and systems for use in preparing the subjectcompositions.

These and other objects, advantages, and features of the invention willbecome apparent to those persons skilled in the art upon reading thedetails of the disclosure as more fully described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in conjunction with the accompanying drawings. It isemphasized that, according to common practice, the various features ofthe drawings are not to-scale. On the contrary, the dimensions of thevarious features are arbitrarily expanded or reduced for clarity.Included in the drawings are the following figures:

FIG. 1 shows a matrix of an exemplary polysaccharide based hydrogel;

FIG. 2 shows the chemical structure for PEG Succinimidyl Succinate;

FIG. 3 shows the chemical structure for PEG Succinimidyl Glutarate;

FIG. 4 shows an exemplary composition of a PEG-PEG-Chitosan hydrogel;

FIG. 5 shows vial of fragmented hydrogel;

FIG. 6 shows an exemplary syringe configuration for rehydration offragmented hydrogel;

FIG. 7 shows an exemplary composition of rehydrated hydrogel.

DETAILED DESCRIPTION OF THE INVENTION

Before the present invention is described, it is to be understood thatthis invention is not limited to particular embodiments described, assuch may, of course, vary. It is also to be understood that theterminology used herein is for the purpose of describing particularembodiments only, and is not intended to be limiting, since the scope ofthe present invention will be limited only by the appended claims.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassedwithin the invention. The upper and lower limits of these smaller rangesmay independently be included or excluded in the range, and each rangewhere either, neither or both limits are included in the smaller rangesis also encompassed within the invention, subject to any specificallyexcluded limit in the stated range. Where the stated range includes oneor both of the limits, ranges excluding either or both of those includedlimits are also included in the invention.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, some potential andpreferred methods and materials are now described. All publicationsmentioned herein are incorporated herein by reference to disclose anddescribe the methods and/or materials in connection with which thepublications are cited. It is understood that the present disclosuresupersedes any disclosure of an incorporated publication to the extentthere is a contradiction.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise. Thus, for example, reference to “acompound” includes a plurality of such compounds and reference to “thepolymer” includes reference to one or more polymer and equivalentsthereof known to those skilled in the art, and so forth.

The publications discussed herein are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present invention isnot entitled to antedate such publication by virtue of prior invention.Further, the dates of publication provided may be different from theactual publication dates which may need to be independently confirmed.

Introduction

In general, the present invention includes hydrogel compositions thathave been fabricated out of a polysaccharide and two or more additionalcomponents. The subject hydrogel compositions are characterized by beingcapable of bonding tissue in both wet (e.g., blood) and dryenvironments, where adhesion of the composition to the tissue isphysiologically acceptable. A further feature of the subjectcompositions is that they are well tolerated and do not elicit asubstantial inflammatory response, if any inflammatory response. Thesubject compositions can provide multiple desirable qualities such as acombination of any of the following: hemostatic properties, adhesiveproperties, re-vascularization, biocompatibility, bactericidal,bacteriostatic and/or fungicidal properties, tissue remodeling and/orprovides a scaffold for tissue engineering, regeneration, and/or cellseeding, enzymatic or hydrolytic degradation pathways, swelling,engineered residence times, engineered viscosities, temperature orenergy activation, inclusion of agents to enable visualization underimaging modalities (X-ray, CT, MRI, US, PET, CTA, etc.), engineereddegree of hydrophilicity or hydrophobicity, gap and/or space filling,surface coating, ability to absorb energy, inclusion of foaming agents,inclusion of visual agents, ability to act as a drug delivery platform,media for sound transmission, and engineered durometer. A fragmentedhydrogel that is sufficiently hydrated possesses flow properties thatare similar to liquid solutions, however, the materials are fully curedand not subject to additional crosslinking reactions once they have beenpackaged for use. Thus, the fragmented hydrogel of the present inventionprovides a means to combine the flowable, conformable characteristics ofthe in situ curing hydrogel formulations with the ease of handling anduse of the fully cured hydrogel formulations.

The subject fragmented polysaccharide based hydrogel compositions areprepared by combining or mixing a polysaccharide element and two or morecomponents, such as a polymer and a cross-linking agent. The compositionis subsequently fragmented to form small pieces of the polymer matrixthat can subsequently be suspended in a solution. An exemplary matrix isprovided in FIG. 1. Each of these precursor components or compositionsis now reviewed separately in greater detail.

Compositions

As noted above, the compositions of the present invention include apolysaccharide component. Examples of polysaccharides suitable for usewith the present invention include, but are not limited to, chitosan,hyaluronic acid, the family of chondroitin sulfates, heparin, keratansulfate, glycogen, glucose, amylase, amylopectin and derivativesthereof. The polysaccharide may be naturally occurring or syntheticallyproduced. Polysaccharides have several reactive groups that areavailable for chemical modification. These include the hydroxyl (OH),carboxyl (COOH), and acetamido (COCH₃) groups. Further functionality canbe imparted to specific polysaccharides in the form of an amine (NH₂)group via basic deacetylation, in which a polysaccharide is exposed tobasic conditions at elevated temperatures. The degree of deacetylationis dependent on the strength of the alkaline conditions, the temperatureof the reaction environment, and the duration of the reaction. Forexample, the percentage of deacetylation can be controlled to obtaindifferent chitosan molecules from a single source of chitin. Othermethods of imparting functionality onto polysaccharides are known to theart, such as the functionalizing of native hyaluronic acid with aminegroups through the use of a hydrazide as taught by Prestwich and Marecakin U.S. Pat. No. 5,874,417, which is herein incorporated by reference.In this method, the carboxyl group of the disaccharide is linked to amulti-functional hydrazide under acidic conditions in the presence of asoluble carbodiimide.

In certain embodiments, the polysaccharide is chitosan. Chitosan is adisaccharide formed through the deacetylation of chitin, a naturallyoccurring material found in crustacean shells and some fungi. Chitosanis a biocompatible, hydrophilic polymer with hemostatic andantimicrobial characteristics. The Chitosan may be from a naturaloccurring source or may be synthetically synthesized. Chitosan isdescribed in detail is U.S. Pat. Nos. 5,836,970, 5,599,916, and6,444,797, the disclosures of which are incorporated by reference hereinin their entirety.

The non-polysaccharide components of the hydrogel material may include ahydrophilic polymer such as any of the following natural, synthetic, orhybrid polymers: poly(ethylene glycol), poly(ethylene oxide), poly(vinylalcohol), poly(allyl alcohol), poly(vinylpyrrolidone), poly(alkyleneoxides), poly(oxyethylated polyols), poly(ethyleneimine),poly(allylamine), poly(vinyl amine), poly(aminoacids),poly(ethyloxazoline), poly(ethylene oxide)-co-poly(propylene oxide)block copolymers, polysaccharides, carbohydrates, oligopeptides, andpolypeptides. The polymer chains may include homo-, co-, or terpolymersof the above materials, in a linear or branched form, and derivativesthereof. These materials may crosslink into a hydrogel through theformation of covalent bonds through the action of chemically activegroups that are present on the polysaccharide and the counterparthydrophilic polymers. Among the chemically active groups that arepreferred for use in the present invention are those that can form acovalent bond with the readily available nucleophilic or electrophilicresidues.

These exemplary materials may crosslink into a hydrogel through theformation of covalent bonds through the action of chemically activegroups that are present on the hydrophilic polymers. Among thechemically active groups that are preferred for use in the presentinvention are those that can form a covalent bond with the readilyavailable nucleophilic or electrophilic residues.

Examples of electrophilic groups that can react with the nucleophilicgroups present on the substrate include but are not limited to carboxylgroups, isocyanates, thiocyanates, N-hydroxysuccinimide esters, glycidylethers, glycidyl epoxides, vinyl sulfones, maleimides, orthopyridyldisulfides, iodoacetamides, and carbodiimides. Examples of nucleophilicgroups that can react with the electrophilic groups present on thesubstrate include but are not limited to anhydrides, primary, secondary,tertiary, or quaternary amines, amides, urethanes, ureas, hydrazides,sulfahydryl groups, or thiols. The preceding list of reactive groupsserves as an illustrative example; extension to other nucleophilic andelectrophilic moieties should be clear to those of skill in the art.

In one embodiment, the hydrogel composition is a three-componenthydrogel that includes a multifunctional PEG with terminal nucleophilicgroups, a multifunctional PEG with terminal electrophilic groups, andchitosan. When the polymeric components are reconstituted with theappropriate buffers and mixed, they react to form a cohesive hydrogel.

The multifunctional PEG with terminal nucleophilic groups may comprise adifunctionally activated, trifunctionally activated, tetrafunctionallyactivated, or a star-branched activated polymer. The molecular weight ofthe multifunctional nucleophilic PEG may be in the range of 1 kiloDalton(kD) to 100 kD; the range of 5 kD to 40 kD; or the range of 10 kD to 20kD. The multifunctional nucleophilic PEG mass be present in masspercentages of at least 1%; at least 5%; at least 10%; at least 20%; atleast 40%; at least 80%; at least 99%.

The multifunctional PEG with terminal electrophilic groups may comprisedifunctionally activated, trifunctionally activated, tetrafunctionallyactivated, or a star-branched activated polymer. The molecular weight ofthe multifunctional electrophilic PEG may be in the range of 1 kD to 100kD; the range of 5 kD to 40 kD; or the range of 10 kD to 20 kD. Themultifunctional electrophilic PEG mass be present in mass percentages ofat least 1%; at least 5%; at least 10%; at least 20%; at least 40%; atleast 80%; at least 99%.

The polysaccharide (e.g., chitosan) may be present in a salt or amineform. The chitosan may have a molecular weight in the range of 10 Daltonto 1 kD; the range of 1 kD to 10 kD; the range of 10 kD to 100 kD; therange of 100 kD to 250 kD; the range of 250 kD to 500 kD; or the rangeof 500 kD to 1000 kD. The chitosan may have a degree of deacetylation inthe range of 1% to 10%; the range of 10% to 20%; the range of 20% to30%; the range of 30% to 40%; the range of 40% to 50%; the range of 50%to 60%; the range of 60% to 70%; the range of 70% to 80%; the range of80% to 90%; or the range of 90% to 99%. The chitosan may be present inthe set hydrogel in a mass percentage range of 0.01% to 0.1%; a range of0.1% to 0.5%; a range of 0.5% to 1.0%; a range of 1.0% to 5%; a range of5% to 10%; a range of 10% to 20%; a range of 20% to 40%; a range of 40%to 80%; or a range of 80% to 99%. In certain embodiments, thepolysaccharide is chitosan. In further embodiments, the chitosan mayalso comprise a derivative of chitosan, such as N,Ocarboxymethylchitosan as described in U.S. Pat. No. 5,888,988, or adicarboxyl derivatized chitosan as described in WO 2009/028965 thedisclosures of which are incorporated herein by reference in theirentirety. For example, dicarboxyl derivatized chitosan may becrosslinked to a polyethylene glycol with at least two nucleophilicreactive groups via a polyethylene glycol with at least twoelectrophilic reactive groups.

An example of a physiologically acceptable polymer that may be suitablefor use in this invention is poly(ethylene glycol) that has beenmodified with a diester to produce a polymer that has a hydrolyticallydegradable ester linkage in its backbone and a terminal ester group thatcan be further modified to enable crosslinking with compatible chemicalgroups. The following examples illustrate the range of hydrolysis ratesthat a hydrogel comprised of these types of polymers is capable ofexhibiting.

Braunova et. al. (Collect. Czech. Chem. Commun. 2004, 69, 1643-1656)have shown that the rate of hydrolysis of ester bonds in poly(ethyleneglycol) polymers decreases as the number of methylene groups that borderthe ester bond is increased. For example, a copolymer of LLL and amulti-armed poly(ethylene glycol) succinimidyl succinate will degrade inapproximately 8 days in aqueous media under physiological conditions. Asshown in FIG. 2, the succinimidyl succinate has two methyl groupslocated next to the hydrolytically susceptible ester bond.

By way of comparison, a copolymer of LLL and a multi-armed poly(ethyleneglycol) succinimidyl glutarate will degrade in approximately 50 days inaqueous media under physiological conditions. As shown in FIG. 3, thesuccinimidyl glutarate has three methyl groups located next to thehydrolytically susceptible ester bond.

As the number of methyl groups neighboring the ester bond increases, therate of hydrolysis of the ester bond decreases. Further decreases in therate of hydrolysis of the ester bond should be attained by increasingthe number of methyl groups in the PEG polymer along the followingprogression: PEG succinimidyl adipate, PEG succinimidyl pimelate, PEGsuccinimidyl suberate, PEG succinimidyl azelate, PEG succinimidylsebacate, etc. The extension of this method of controlling degradationtimes to other systems should be readily accessible to one of skill inthe art.

The degradation time of the synthetic PEG hydrogels can be also bemodified without changing the chemical structure of the underlyingpolymer components. This situation would arise in the event that adegradation time that is in between the degradation times of two of thepolymers listed above. For example, a hydrogel comprised of a 4 armed,10 kiloDalton, PEG-succinimidyl succinate polymer and trilysine (SS-LLL)degrades in approximately 7 days when exposed to an aqueous medium at37° C. A hydrogel comprised of a 4 armed, 10 kiloDalton,PEG-succinimidyl glutarate polymer and trilysine (SG-LLL) degrades inapproximately 50 days when exposed to an aqueous medium at 37° C. If ahydrogel with a degradation time of approximately 14 days was desired,there are several methods that may be applied to achieve thatdegradation time using the polymers listed in this example. One methodis to fabricate a hydrogel in which the reactive electrophilic groupsare provided by a blend of the two PEG polymers and the nucleophilicgroups are provided by the trilysine. The stoichiometric blend of thetwo PEG polymers may be altered to provide the desired degradation time.For example, a blend of PEG polymers in which 65% of the requiredelectrophilic groups are provided by the PEG succinimidyl succinate and35% of the required electrophilic groups are provide by the PEGsuccinimidyl glutarate can be combined with trilysine (while maintaininga 1:1 nucleophilic group:electrophilic group stoichiometric ratio) toform a hydrogel that degrades in approximately 14 days when exposed toan aqueous medium at 37° C.

A second method of obtaining an intermediate degradation time would beto vary the stoichiometric ratio of reactive nucleophilic groups toreactive electrophilic groups within the hydrogel precursor polymers.This may be done for hydrogels in which the nucleophilic groups areprovided by multiple donors, for hydrogels in which the nucleophilicgroups are provided by a single donor, for hydrogels in which theelectrophilic groups are provided by multiple donors, for hydrogels inwhich the electrophilic groups are provided by single donors, or anycombination thereof.

A third method of obtaining an intermediate degradation time would be tovary the amount of polymer in the hydrogel. For example, if a givenhydrogel contained 5% polymeric content by weight at equilibrium, thedegradation time of said hydrogel may be extended by increasing thepolymeric content to a value above 5% by weight at equilibrium.Similarly, the degradation time of said hydrogel may be reduced bydecreasing the polymeric content to a value below 5% by weight atequilibrium.

A non-degradable formulation may be obtained by using a PEG basedpolymer that does not degrade under physiological conditions, such as apolymer fabricated from PEG diacrylate or other similar polymers.

Another form of the invention is a three-component hydrogel comprised ofa multifunctional PEG with terminal nucleophilic groups, an aldehydecomponent, and chitosan. When the polymeric components are reconstitutedwith the appropriate buffers and mixed, they react to form a cohesivehydrogel.

The nucleophilic PEG and polysaccharide (e.g., chitosan) components inthe composition are as described earlier. The aldehyde component in thecomposition as provided herein can be any biocompatible aldehyde withlow toxicity. In particular, the aldehyde component includes adi-aldehyde, a polyaldehyde or a mixture thereof. The examples of thealdehyde include, but are not limited to, glyoxal, chondroitin sulfatealdehyde, succinaldehyde, glutaraldehyde, and malealdehyde. In someembodiments, the aldehyde component is glutaraldehyde. Other suitablealdehydes which have low toxicity include multifunctional aldehydesderived from naturally-occurring substances, e.g., dextrandialdehyde, orsaccharides. The aldehyde component can be an aldehyde product obtainedby an oxidative cleavage of carbohydrates and their derivatives withperiodate, ozone or the like. The aldehyde may optionally be pre-treatedwith heat. See U.S. Pat. No. 7,303,757 by Schankereli for “Biocompatiblephase invertable proteinaceous compositions and methods for making andusing the same”, incorporated by reference herein in its entirety. Thealdehyde component can be analyzed for properties such as, viscosity,and osmolality. The aldehyde component of an adhesive composition canitself be further comprised of components and/or sub-components. Thus,the aldehyde component can be described in terms of weight,weight-to-weight, weight-to-volume, or volume-to-volume, either beforeor after mixing. For example, a polysaccharide may be crosslinked to amultifunctional synthetic polymer with at least two reactivenucleophilic groups via a dextran derivatized with aldehyde groups.

In some embodiments, the aldehyde component comprises of about 1-90%aldehyde concentration. In some embodiments, the aldehyde componentcomprises of about 1-75% aldehyde concentration. In some embodiments,the aldehyde component comprises of about 5-75% aldehyde concentration;about 10-75% aldehyde concentration; about 20-75% aldehydeconcentration; about 30-75% aldehyde concentration; about 40-75%aldehyde concentration; about 50-75% aldehyde concentration; or about60-75% aldehyde concentration.

The composition can comprise at least about 1% aldehyde concentration;at least about 5% aldehyde concentration; at least about 10% aldehydeconcentration; at least about 20% aldehyde concentration; at least about30% aldehyde concentration; at least about 40% aldehyde concentration;at least about 50% aldehyde concentration; at least about 60% aldehydeconcentration; at least about 70% aldehyde concentration; at least about80% aldehyde concentration; at least about 90% aldehyde concentration;or at least about 99% aldehyde concentration. In some embodiments, theadhesive composition comprises of about 1-30%, about 25-75%, about50-75% or about 75-99% aldehyde concentration.

In some embodiments, the composition comprises of at least about 1%glutaraldehyde concentration; at least about 5% glutaraldehydeconcentration; at least about 8% glutaraldehyde concentration; at leastabout 10% glutaraldehyde concentration; at least about 20%glutaraldehyde concentration; at least about 30% glutaraldehydeconcentration; at least about 40% glutaraldehyde concentration; at leastabout 50% glutaraldehyde concentration; at least about 60%glutaraldehyde concentration; at least about 70% glutaraldehydeconcentration; at least about 80% glutaraldehyde concentration; at leastabout 90% glutaraldehyde concentration; or at least about 99%glutaraldehyde concentration. In some embodiments, the compositioncomprises about 1-30%, about 25-75%, about 50-75% or about 75-99%glutaraldehyde concentration.

Thickening agents may be added to the forms of the invention describedabove. The thickening agents include, for example, dextran,carboxymethyl cellulose, polyethylene glycol, liposomes, proliposomes,glycerol, starch, carbohydrates, povidone, polyethylene oxide, andpolyvinyl alcohol. In some embodiments, the thickening agent is dextran,polyethylene glycol or carboxymethyl cellulose. In some embodiments, thecomposition comprises at least about 1% thickening agent concentration;at least about 5% thickening agent concentration; at least about 10%thickening agent concentration; at least about 20% thickening agentconcentration; at least about 30% thickening agent concentration; atleast about 40% thickening agent concentration; at least about 50%thickening agent concentration; at least about 60% thickening agentconcentration; at least about 70% thickening agent concentration; atleast about 80% thickening agent concentration; or at least about 90%thickening agent concentration. In some embodiments, the compositioncomprises at least about 0.5%-10%, at least about 0.5%-25%, or at leastabout 0.5%-50% thickening agent concentration. In some embodiments, thethickening agent can comprise at least about 0.5% of the composition.The thickening agent can alter a gel time of the composition.

Some embodiments of the aforementioned aspects of the present inventionmay further comprise a radiopaque material. The radiopaque materialincludes, for example, bismuth oxide (Bi₂O₃), zinc oxide (ZnO), bariumsulfate (BaSO₄) lanthanum oxide (La₂O₃), cerium oxide (CeO2), terbiumoxide, ytterbium oxide, neodymium oxide, zirconia (ZrO₂), strontia(SrO), tin oxide (SnO₂), radiopaque glass and silicate glass. Theradiopaque glass includes, for example, barium silicate, silico-aluminobarium or strontium containing glass. The silicate glass includes, forexample, barium or strontium containing glass. In some embodiments, theradiopaque material comprises at least about 0.001%; at least about0.05%; at least about 0.1%; at least about 0.2%; at least about 0.5%; atleast about 1%; at least about 2%; at least about 5%; at least about 8%;or at least about 10% of the adhesive composition.

The hydrogel compositions as provided herein can optionally contain avariety of naturally occurring or synthetically produced additives suchas, but not limited to, water, buffer, saline solution, neutral salt,carbohydrate, fiber, miscellaneous biological material, wetting agent,antibiotics, preservative, dye, thickening agent, thinning agent,fibrinogen, polymer such as polyethylene glycol or combination thereof.Polymers include synthetic polymers such as, polyamides, polyesters,polystyrenes, polyacrylates, vinyl polymers (e.g., polyethylene,polytetrafluoro-ethylene, polypropylene and polyvinyl chloride),polycarbonates, polyurethanes, poly dimethyl siloxanes, celluloseacetates, polymethyl methacrylates, ethylene vinyl acetates,polysulfones, nitrocelluloses and similar copolymers. Polymers furtherinclude biological polymers which can be naturally occurring or producedin vitro by fermentation and the like. Biological polymers include,without limitation, collagen, elastin, silk, keratin, gelatin, polyaminoacids, polysaccharides (e.g., cellulose and starch) and copolymersthereof.

Flexibilizers can be included in the hydrogel composition to provideflexibility to the material bond upon curing. Flexibilizers may benaturally occurring compositions or synthetically produced. Suitableflexiblizers include synthetic and natural rubbers, synthetic polymers,natural non-native biocompatible proteins (such as exogenous (i.e.,non-native) collagen and the like), glycosaminoglycans (GAGs) (such ashyaluronin and chondroitin sulfate), and blood components (such asfibrin, fibrinogen, albumin and other blood factors).

The composition as provided herein can optionally include salts and/orbuffers. Examples of the salt include, but are not limited to, sodiumchloride, potassium chloride and the like. Suitable buffers can include,for example, ammonium, phosphate, borate, bicarbonate, carbonate,cacodylate, citrate, and other organic buffers such astris(hydroxymethyl) aminomethane (TRIS), morpholine propanesulphonicacid (MOPS), and N-(2-hydroxyethyl) piperazine-N′(2-ethanesulfonic acid)(HEPES). Suitable buffers can be chosen based on the desired pH rangefor the hydrogel composition.

Additional additives may be present in the formulation to modify themechanical properties of the composition. Some additives include, forexample, fillers, softening agents and stabilizers. Examples of fillersinclude, but are not limited to, carbon black, metal oxides, silicates,acrylic resin powder, and various ceramic powders. Examples of softeningagents include, but are not limited to, dibutyl phosphate,dioctylphosphate, tricresylphosphate, tributoxyethyl phosphates andother esters. Examples of stabilizers include, but are not limited to,trimethyldihydroquinone, phenyl-β-naphthyl amine,p-isopropoxydiphenylamine, diphenyl-p-phenylene diamine and the like.

One class of additives that may be included in the composition isnanoparticles or nanometer scale constructions. An example ofnanoparticles that have been engineered to have specific physicalcharacteristics are nanoshells, as taught by Oldenburg et. al. (U.S.Pat. No. 6,344,272, incorporated herein by reference in its entirety).Nanoshells are comprised of a metallic shell surrounding anon-conducting core; by varying the diameter of the core and thethickness of the shell, the absorption wavelength of the materials canbe tuned to specific regions of the spectrum. West et. al. discloses theincorporation of nanoshells into a thermally sensitive polymer matrixfor drug delivery in U.S. Pat. Nos. 6,428,811 and 6,645,517, and furtherteaches the use of nanoshells to treat tumors through localizedhyperthermia in U.S. Pat. No. 6,530,994 (the above patents are hereinincorporated by reference in their entirety). The combination ofnanoparticles or other nanoscale structures with the composition of theinvention may provide additional functionality (i.e. tunable absorptionspectra) to the composition. In one example, the composition may beemployed to fix the nanoparticles tuned to absorb near infrared light ina desired physical position prior to the application of a near-infraredlaser to induce local hyperthermia. The incorporation of the nanoshellsin the hydrogel matrix prevents the leaching of the nanoshells away fromthe target area.

The composition may also optionally include a plasticizing agent. Theplasticizing agent provides a number of functions, including wetting ofa surface, or alternately, increasing the elastic modulus of thematerial, or further still, aiding in the mixing and application of thematerial. Numerous plasticizing agents exist, including fatty acids,e.g., oleic acid, palmitic acid, etc., dioctylphtalate, phospholipids,and phosphatidic acid. Because plasticizers are typically waterinsoluble organic substances and are not readily miscible with water, itis sometimes advantageous to modify their miscibility with water, bypre-mixing the appropriate plasticizer with an alcohol to reduce thesurface tension associated with the solution. To this end, any alcoholmay be used. In one representative embodiment of this invention, oleicacid is mixed with ethanol to form a 50% (w/w) solution and thissolution then is used to plasticize the polymer substrate during theformulation process. Whereas the type and concentration of theplasticizing agent is dependent upon the application, in certainembodiments the final concentration of the plasticizing agent is fromabout 0.01 to 10% (w/w), including from about 2 to about 4% (w/w). Otherplasticizing agents of interest include, but are not limited to:polyethylene glycol, glycerin, butylhydroxytoluene, etc.

Fillers of interest include both reinforcing and non-reinforcingfillers. Reinforcing fillers may be included, such as chopped fibroussilk, polyester, PTFE, NYLON, carbon fibers, polypropylene,polyurethane, glass, etc. Fibers can be modified, e.g., as describedabove for the other components, as desired, e.g., to increasewettability, mixability, etc. Reinforcing fillers may be present fromabout 0 to 40%, such as from about 10 to about 30%. Non-reinforcingfillers may also be included, e.g., clay, mica, hydroxyapatite, calciumsulfate, bone chips, etc. Where desired, these fillers may also bemodified, e.g., as described above. Non-reinforcing fillers may bepresent from about 0 to 40%, such as from about 10 to about 30%.

In certain embodiments, the composition may include a foaming agentwhich, upon combination with the crosslinker composition, results in afoaming composition, e.g., compositions that includes gaseous airbubbles interspersed about. Any convenient foaming agent may be present,where the foaming agent may be an agent that, upon contact with thecrosslinking composition, produces a gas that provides bubble generationand, hence, the desired foaming characteristics of the composition. Forexample, a salt such as sodium bicarbonate in an amount ranging fromabout 2 to about 5% w/w may be present in the substrate. Uponcombination of the substrate with an acidic crosslinker composition,e.g., having a pH of about 5, a foaming composition is produced.

Biologically active agents may be incorporated into the polymer networkof the invention; these agents include but are not limited to plasmaproteins, hormones, enzymes, antibiotics, antiseptic agents,antineoplastic agents, antifungal agents, antiviral agents,anti-inflammatory agents, growth factors, anesthetics, steroids, cellsuspensions, cytotoxins, cell proliferation inhibitors, and biomimetics.The biologically active agents can be incorporated into the hydrogel ofthe invention by any means known in the art. As a non-limiting example,an agent or multiple agents may be added to the component solutionsprior to mixing such that the hydrogel matrix forms around the agent ormultiple agents and mechanically encapsulates the agent or agents.Alternatively, the agent or agents may be added to one or all of thecomponent solutions prior to mixing. In another example, the agent oragents may be modified or derivatized to react with the components ofthe hydrogel and form covalent bonds with the hydrogel. The agent oragents may be bonded to the backbone of the hydrogel structure in apendent chain configuration or as a fully integrated component of thehydrogel structure. In yet another example, the agent or agents may besuspended within a hydrophobic domain encapsulated within or distributedthroughout the hydrogel. Alternatively, the agent or agents may beassociated with the backbone of hydrogel through electrostatic, van DerWalls, or hydrophobic interactions. Combinations of any of theaforementioned techniques are also contemplated (e.g. a negativelycharged agent that is physically encapsulated in a positively chargedhydrogel matrix). The exact means of incorporation will be dictated bythe nature of the biologically active agent.

Methods

The hydrogel may be fabricated in a manner suitable to its respectivecomponents. For example, a hydrogel comprised of a multi-armedamine-terminated PEG, a chitosan, and a multi-armed ester-terminated PEGmay be fabricated by combining the three polymers in a 1:1 functionalgroup molar ratio at a 10% mass fraction in an aqueous basic buffer.

Fragmentation

The term “fragment” refers to a process by which a single, whole,polymeric material is broken into smaller pieces that retain thematerial properties of the parent material. This may be accomplished bya number of methods, including syringe to syringe mixing of flowablepolymer materials, maceration of the polymer material with blades,rotors, hammers, ultrasonic vibrations, or other suitable techniques,filing, sanding, grating, and grinding and/or milling processes, such ascone and gyratory crushing, disk attrition milling, colloid and rollmilling, screen milling and granulation, hammer and cage milling, pinand universal milling, jet or fluid energy milling, impact milling andbreaking, jaw crushing, roll crushing, disc milling, and verticalrolling, including cryogenic grinding and/or cryogenic milling.

Cryogenic milling or cryogenic grinding refers to a process by whichsamples are chilled in liquid nitrogen and pulverized to reduce them toa desired particulate size. Cooling samples to approximately −200° C.serves to make flexible samples more brittle and susceptible togrinding. The low temperature also preserves characteristics of thesample that may be lost to the higher temperatures that are present intraditional grinding or milling processes. For example, this can beaccomplished by placing the sample in a sealed container along with amagnetically active impactor. The sealed container can then be immersedin a chamber of liquid nitrogen that is surrounded by a magnetic coil.The coil may then be activated once the temperature of the samplereaches approximately −200° C., shuttling the impactor back and forthwithin the container to pulverize the sample. The size of theparticulate can be controlled by varying the length of each grindingsession and/or conducting multiple grinding sessions. The samplecontainer may be cooled between grinding sessions to maintain anadequately cool temperature.

Another example of cryogenic milling or grinding uses liquid nitrogen inconjunction with a stirred ball mill. In this method, the sample ofinterest is loaded into the drum of the stirred ball mill along withgrinding media of choice. The type of media may vary according to thedesired results of the grinding process (particulate surface area,aspect ratio, shape, compactability, dispersion stability, opacity,flowability, etc.) and the material characteristics of the sample.Typical examples of grinding media include through-hardened steel shot,zirconium silicate, zirconium oxide, flint stones, alumina, siliconnitride, mullite, tungsten carbide, ceramic, chrome steel, glass,silicon carbide, stainless steel, and carbon steel. The size of thegrinding media may also vary according to the requirements of thespecific grinding process. This listing is not complete, and theidentities of additional grinding media should be readily accessible toone of skill in the art. The drum is then sealed and the temperature ofthe drum is lowered to cryogenic temperatures by flowing liquid nitrogenthrough a jacket that surrounds the exterior of the drum. Once thecontents of the drum have dropped to a sufficient temperature, a shaftrunning through the center of the drum begins rotating. Arms or discsattached to the shaft agitate the sample and media, pulverizing thesample to the desired size (or alternative specification).

Another cryogenic grinding technique that may be used is to use liquidnitrogen to cool the drum of a conventional ball mill. In this method,the sample and media are loaded into a drum and cooled as described forthe stirred ball mill, above. Once a sufficiently depressed drumtemperature has been attained, the drum itself is rotated to provide theshear and impact forces necessary for sample fragmentation. Other typesof fragmenting that may be amiable to cryogenic processing include, butare not limited to, cone and gyratory crushing, disk attrition milling,colloid and roll milling, screen milling and granulation, hammer andcage milling, pin and universal milling, jet or fluid energy milling,impact milling and breaking, jaw crushing, roll crushing, disc milling,and vertical rolling.

This list does not encompass the entirety of the potential methods offragmenting a whole polymer into smaller particles. The applicability ofother methods should be readily accessible to one of skill in the art.

Drying

The hydrogel may be dried before or after being subjected tofragmentation. The term “drying” refers to any process by which thewater content of a candidate polymer material is reduced from an initialvalue to a lower value. This may be accomplished by placing the materialin an environment with lower water content than the polymer materialunder various temperature and pressure conditions, some of which arelisted in Table 1

TABLE 1 Temperature Pressure Example Ambient Ambient Air drying ElevatedAmbient Oven drying Ambient Negative Vacuum drying Elevated NegativeVacuum oven drying Reduced Negative Freeze drying

Application of drying techniques beyond those listed herein should bereadily accessible to one of skill in the art. For example, US.Published Pat. App. No. 2007/0231366 teaches a method of drying ahydrogel that comprises halting a solution of components undergoingcrosslinking reaction prior to the completion of the reaction byreducing the temperature of the solution below the freezing point of thereacting solution, then subsequently freeze drying thepartially-crosslinked hydrogel to remove the solvent from the partiallycrosslinked hydrogel. The partially crosslinked hydrogel is thenprocessed through a series of treatments that serve to complete thecrosslinking reaction. The reliance of this method of fabrication on aphase change between liquid and solid is cumbersome, and places limitson the production methods that can be employed in fabricated hydrogelsby the taught method. For example, the timing of the transition of thesolution from a liquid to solid state (i.e. freezing) is highlydependent on the physical and material characteristics of the mold (wallthickness, heat transfer coefficient, hydrophilicity or hydrophobicityof the mold surface), the freezing method (cold plate, freezer,immersion in liquid nitrogen, etc.), and the rate of the crosslinkingreaction among others. Maintaining a consistent process in the face ofthese variables is challenging and can provide an obstacle to thescaled-up production of a hydrogel via the taught method.

One method for reducing the complexity of the process taught in US.Published Pat. App. No. 2007/0231366 is to use a method for halting orslowing the rate of the crosslinking reaction that is not subject to asmany parameters as freezing, such as changing the pH of the solution ofreacting components to a level that does not support furthercrosslinking. For example, the reaction rate of a second-ordernucleophilic substitution between an N-hydroxysuccinimide and a primaryamine accelerates as the pH of the reaction media becomes more alkalineand decelerates as the pH of the reaction media becomes more acidic.Therefore, the addition of an aliquot of an acidic solution at asufficient molarity and volume to shift the pH of the reacting media toan acidic condition will halt or slow the reaction rate of thenucleophilic substitution. Yet another means of changing the rate ofreaction is changing the ionic strength of the reaction media. Thesolution of hydrogel components is then ready for freeze drying. Thebenefit of this novel method is that the alteration of the reaction ratecan be conducted while the hydrogel components are in the liquid phase(e.g. at room temperature), and is not dependent on the size, shape, ormaterial of the casting mold. The independence of the method from theaforementioned limitations will improve consistency of batch-to-batchproduction lots by reducing the complexity and user-dependence of theprocess steps and lends itself to scale-up production by simplifying theuse of larger molds.

After fragmentation, the resultant collection of polymer particulate maybe sorted to achieve a specific distribution of particle sizes. This maybe achieved by passing dry polymeric material through a set of sieves,running water soluble polymeric material through a size exclusioncolumn, or other commonly employed sorting techniques.

In one example, the hydrogel is fabricated in an appropriate reactionmedium, then dried and fragmented using an appropriate method. The dryparticulate can then be loaded into a suitable carrier or deliverydevice. At the time of use, sterile saline can be introduced to the drymaterial to rehydrate it into a solution of suspended hydrogelparticulate. In a second example, the polymer is fabricated in anappropriate reaction medium, fragmented to a desired size, and driedprior to loading into a suitable carrier or delivery device. Again,sterile saline can be introduced to the dry material at the time of useto rehydrate it into a solution of suspended hydrogel particulate.

Rehydration in Appropriate Media

The process of rehydrating the particulate with an appropriate bufferallows the physical characteristics of the resulting slurry to becontrolled. For example, a fragmented hydrogel that is susceptible tohydrolysis under basic conditions may be rehydrated in an acidic aqueousbuffer to extend the functional lifetime of the slurry. In anotherexample, the consistency of the slurry may be adjusted from a thickpaste to a thin, flowable, liquid by adjusting the mass fraction ofdried materials in the reconstituted solution.

In one embodiment of the invention, the polysaccharide and syntheticpolymer are dissolved in a neutral or basic buffer. The crosslinker isdissolved in an appropriately pH balanced buffer. The two solutions arecombined to allow the formation of a hydrogel network between thepolysaccharide, the synthetic polymer, and the crosslinker. The hydrogelis then air-dried to a constant weight and subjected to cryomilling orcryogrinding to produce a collection of particles with a distribution ofparticle sizes.

In a second embodiment of the invention, the polysaccharide andsynthetic polymer are dissolved in a neutral or basic buffer. Thecrosslinker is dissolved in an appropriately pH balanced buffer. The twosolutions are combined to allow the formation of a hydrogel networkbetween the polysaccharide, the synthetic polymer, and the crosslinker.The hydrogel is then fragmented via syringe-to-syringe mixing and storedin the partially-hydrated state. Alternatively, the hydrogel may beplaced in an appropriate aqueous media to swell for a specified lengthof time, or until a specified magnitude of swelling has been attained,prior to fragmenting via syringe-to-syringe mixing. The swelling mediamay comprise but is not limited to thickening agents, radiopaque agents,preservatives, dyes, thinning agents, flexiblizers, salts and orbuffers, fillers, softening agents, stabilizers, nanoparticles,plasticizing agents, biologically active agents, pharmaceutically activeagents, and the like.

In a third embodiment of the invention, the polysaccharide and syntheticpolymer are dissolved in a neutral or basic buffer. The crosslinker isdissolved in an acidic or neutral buffer along with a steroid orsteroids (e.g. triamcinolone, mometasone furoate monohydrate,hydrocortisone, etc.). The two solutions are combined to allow theformation of a hydrogel network between the polysaccharide, thesynthetic polymer, and the crosslinker that entraps the steroid orsteroids. Steroids are generally insoluble in basic or alkalinesolutions, therefore the addition of a steroid to the neutral to acidicbuffer containing the crosslinker acts to prevent or mitigate theprecipitation of the steroid out of solution prior the incorporation ofthe steroid into the hydrogel. The hydrogel is then air-dried to aconstant weight and subjected to cryomilling or cryogrinding to producea collection of particles with a distribution of particle sizes that areloaded with the steroid or steroids. The dry particulate is sievedthrough a series of filters to isolate a desired range of particlesizes, and placed into an aqueous solution at a neutral or acidic pH.The rehydrated slurry may be used in that state to deliver the steroidor steroids to the target anatomy of interest wherein the drug releaseprofile of the steroid is dictated by either the diffusion of thesteroid out of the hydrogel, or the hydrolytic or enzymatic degradationof the fragmented hydrogel (in the case of a hydrogel fabricated withhydrolytically and/or enzymatically degradable linkages), or both. Theslurry may be further combined with another solution comprising, forexample, a thickening agent to result in a viscous solution ofsteroid-loaded particulate that resists diffusion and/or migration awayfrom the point of delivery.

Alternatively, the polysaccharide and synthetic polymer are dissolved ina neutral or basic buffer. The crosslinker is dissolved in anappropriately pH balanced buffer. The two solutions are combined toallow the formation of a hydrogel network between the polysaccharide,the synthetic polymer, and the crosslinker. The hydrogel is thenair-dried to a constant weight and subjected to cryomilling orcryogrinding to produce a collection of particles with a distribution ofparticle sizes. The dry particulate is sieved through a series offilters to isolate a desired range of particle sizes, and placed into anaqueous solution at a neutral or acidic pH comprising a steroid orsteroids to swell. The rehydrated slurry may be used in that state todeliver the steroid or steroids to the target anatomy of interest, orfurther modified to incorporate additional components including but notlimited to radiopaque agents, preservatives, dyes, thinning agents,flexiblizers, salts and or buffers, fillers, softening agents,stabilizers, nanoparticles, plasticizing agents, biologically activeagents, pharmaceutically active agents, and the like.

In a fourth embodiment, the polysaccharide and synthetic polymer aredissolved in a neutral or basic buffer. The crosslinker is dissolved inan acidic to neutral buffer along with an anesthetic (e.g. lidocaine,bupivacaine, xylocaine, etc.). The two solutions are combined to allowthe formation of a hydrogel network between the polysaccharide, thesynthetic polymer, and the crosslinker that entraps the steroid orsteroids. Anesthetics are typically formulated in acidic buffers,therefore the addition of an anesthetic to the neutral to acidic buffercontaining the crosslinker follows current formulary practice. Thehydrogel is then air-dried to a constant weight and subjected tocryomilling or cryogrinding to produce a collection of particles with adistribution of particle sizes that are loaded with the steroid orsteroids. The dry particulate is sieved through a series of filters toisolate a desired range of particle sizes, and placed into an aqueoussolution at a neutral or acidic pH. The rehydrated slurry may be used inthat state to deliver the anesthetic to the target anatomy of interestwherein the drug release profile of the anesthetic is dictated by eitherthe diffusion of the steroid out of the hydrogel, or the hydrolytic orenzymatic degradation of the fragmented hydrogel (in the case of ahydrogel fabricated with hydrolytically and/or enzymatically degradablelinkages), or both. The slurry may be further combined with anothersolution comprising, for example, a thickening agent to result in aviscous solution of an anesthetic-loaded particulate that resistsdiffusion and/or migration away from the point of delivery.

Alternatively, the polysaccharide and synthetic polymer are dissolved ina neutral or basic buffer. The crosslinker is dissolved in anappropriately pH balanced buffer. The two solutions are combined toallow the formation of a hydrogel network between the polysaccharide,the synthetic polymer, and the crosslinker. The hydrogel is thenair-dried to a constant weight and subjected to cryomilling orcryogrinding to produce a collection of particles with a distribution ofparticle sizes. The dry particulate is sieved through a series offilters to isolate a desired range of particle sizes, and placed into anaqueous solution at a neutral or acidic pH comprising an anesthetic toswell. The rehydrated slurry may be used in that state to deliver theanesthetic to the target anatomy of interest, or further modified toincorporate additional components including but not limited tothickeners, radiopaque agents, preservatives, dyes, thinning agents,flexiblizers, salts and or buffers, fillers, softening agents,stabilizers, nanoparticles, plasticizing agents, biologically activeagents, pharmaceutically active agents, and the like.

In a fifth embodiment, the polysaccharide and synthetic polymer aredissolved in a neutral or basic buffer. The crosslinker is dissolved inan acidic to neutral buffer along with an antibiotic (e.g. gentamicin,cephalexin, cefaclore, etc.). The two solutions are combined to allowthe formation of a hydrogel network between the polysaccharide, thesynthetic polymer, and the crosslinker that entraps the steroid orsteroids. Antibiotics are typically formulated in acidic buffers,therefore the addition of an anesthetic to the neutral to acidic buffercontaining the crosslinker follows current formulary practice. Thehydrogel is then air-dried to a constant weight and subjected tocryomilling or cryogrinding to produce a collection of particles with adistribution of particle sizes that are loaded with the steroid orsteroids. The dry particulate is sieved through a series of filters toisolate a desired range of particle sizes, and placed into an aqueoussolution at a neutral or acidic pH. The rehydrated slurry may be used inthat state to deliver the antibiotic to the target anatomy of interestwherein the drug release profile of the antibiotic is dictated by eitherthe diffusion of the antibiotic out of the hydrogel, or the hydrolyticor enzymatic degradation of the fragmented hydrogel (in the case of ahydrogel fabricated with hydrolytically and/or enzymatically degradablelinkages), or both. The slurry may be further combined with anothersolution comprising, for example, a thickening agent to result in aviscous solution of an antibiotic-loaded particulate that resistsdiffusion and/or migration away from the point of delivery.

Alternatively, the polysaccharide and synthetic polymer are dissolved ina neutral or basic buffer. The crosslinker is dissolved in anappropriately pH balanced buffer. The two solutions are combined toallow the formation of a hydrogel network between the polysaccharide,the synthetic polymer, and the crosslinker. The hydrogel is thenair-dried to a constant weight and subjected to cryomilling orcryogrinding to produce a collection of particles with a distribution ofparticle sizes. The dry particulate is sieved through a series offilters to isolate a desired range of particle sizes, and placed into anaqueous solution at a neutral or acidic pH comprising an antibiotic toswell. The rehydrated slurry may be used in that state to deliver theantibiotic to the target anatomy of interest, or further modified toincorporate additional components including but not limited tothickeners, radiopaque agents, preservatives, dyes, thinning agents,flexiblizers, salts and or buffers, fillers, softening agents,stabilizers, nanoparticles, plasticizing agents, biologically activeagents, pharmaceutically active agents, and the like.

In a sixth embodiment, the polysaccharide and synthetic polymer aredissolved in a neutral or basic buffer. The crosslinker is dissolved inan appropriately pH balanced buffer. The two solutions are combined toallow the formation of a hydrogel network between the polysaccharide,the synthetic polymer, and the crosslinker. The hydrogel is thenair-dried to a constant weight and subjected to cryomilling orcryogrinding to produce a collection of particles with a distribution ofparticle sizes. The dry particulate is sieved through a series offilters to isolate a desired range of particle sizes, and is employed asa carrier for platelet-rich-plasma (PRP). The dry particulate iscombined with a solution of PRP to absorb the PRP into the intersticesof the hydrogel network. The rehydrated slurry may be used in that stateto deliver the PRP to the target anatomy, such as a soft tissue defect(e.g. tendon, ligament, hernia, rotator cuff, etc.), a laceration orexternal wound bed (e.g. pressure sore, diabetic ulcer, etc.), or a hardtissue defect (e.g. bone) over a specified period of time. Calcium,thrombin or collagen may be added to the rehydrated slurry activate therelease of growth factors from the PRP. The slurry may be furthermodified to incorporate additional components including but not limitedto thickeners, radiopaque agents, preservatives, dyes, thinning agents,flexiblizers, salts and or buffers, fillers, softening agents,stabilizers, nanoparticles, plasticizing agents, biologically activeagents, pharmaceutically active agents, and the like.

It should be clear that the examples of incorporating the steroid,anesthetic, antibiotic, and PRP into the composition of the inventioncan be extended to any pharmaceutically or biologically active agent,including but not limited to naturally occurring or syntheticallyproduced plasma proteins, hormones, enzymes, antiseptic agents,antineoplastic agents, antifungal agents, antiviral agents,anti-inflammatory agents, human and non human derived growth factors,anesthetics, cell suspensions, cytotoxins, cell proliferationinhibitors, fibrin, fibrinogen, collagen, and biomimetics.

In a seventh embodiment, the polysaccharide and synthetic polymer aredissolved in a neutral or basic buffer. The crosslinker is dissolved inan appropriately pH balanced buffer. The two solutions are combined toallow the formation of a hydrogel network between the polysaccharide,the synthetic polymer, and the crosslinker. The hydrogel is thenvacuum-dried to a constant weight and subjected to cryomilling orcryogrinding to produce a collection of particles with a distribution ofparticle sizes. The dry particulate is sieved through a series offilters to isolate a desired range of particle sizes and rehydrated in aneutral solution of chitosan to produce a flowable slurry. The viscosityof the slurry can be adjusted by changing the mass percentage of dryparticulate or changing the concentration of the chitosan in therehydrating solution. Alternatively, a second component (e.g. dextran)may be added to the rehydrating solution as a thickening agent. Theslurry may be further modified to incorporate additional componentsincluding but not limited to radiopaque agents, preservatives, dyes,thinning agents, flexiblizers, salts and or buffers, fillers, softeningagents, stabilizers, nanoparticles, plasticizing agents, biologicallyactive agents, pharmaceutically active agents, and the like.

In an eighth embodiment, the polysaccharide and synthetic polymer aredissolved in a neutral or basic buffer. The crosslinker comprises ahydrolytic domain that degrades upon exposure to water, and is dissolvedin an acidic buffer. The two solutions are combined to allow theformation of a hydrogel network between the polysaccharide, thesynthetic polymer, and the crosslinker. The hydrogel is thenvacuum-dried to a constant weight and subjected to cryomilling orcryogrinding to produce a collection of particles with a distribution ofparticle sizes. The dry particulate is sieved through a series offilters to isolate a desired range of particle sizes and rehydrated inan acidic solution to slow or halt the hydrolysis of the crosslinker andassociated degradation of the hydrogel prior to use. The viscosity ofthe slurry can be adjusted by changing the mass percentage of dryparticulate or through the incorporation of a second component (e.g.dextran) as a thickening agent. The slurry may be further modified toincorporate additional components including but not limited toradiopaque agents, preservatives, dyes, thinning agents, flexiblizers,salts and or buffers, fillers, softening agents, stabilizers,nanoparticles, plasticizing agents, biologically active agents,pharmaceutically active agents, and the like.

Utility

The compositions described herein may combine multiple utilities asdescribed below. For example, the hydrogel may be used as an embolic foraneurysmal closure. The composition may be used for the occlusion ofneurovascular and/or peripheral aneurysm or the occlusion of Fallopiantubes and/or seminal vesicles for sterilization. Additional applicationsof the composition on the invention are in varicose vein embolization,uterine fibroid embolization, embolization of hypervascularized tumors,embolization of arterio-venous malformations, meningioma embolization,paraganglioma tumor embolization, and metastatic tumor embolization astaught in U.S. Pat. No. 7,670,592 and herein incorporated by referencein its entirety. The treatment of tumors may or may not includechemotherapeutic agents as a component of the hydrogel.

The composition may be used as a hemostat. One application of theinvention is the management of broken, burned, or lacerated mucosallinings, such as the tonsils post tonsillectomy, adenoids postadenoidectomy, after tooth removal, to treat dental dry socket, to treatepistaxis, or treat disruption of any other mucosal surfaces wherebleeding control is required. The composition may be used to providehemostatic control post removal of tissue for biopsy purposes asexperienced in liver, lung, kidney, breast, soft tissue, and lymph nodebiopsies as taught in U.S. Pat. Nos. 5,080,655, 5,741,223, 5,725,498,and 6,071,301. All patents listed in the preceding paragraph are hereinincorporated by reference in their entirety.

The composition may be used to act as an agent for the treatment ofdiabetic foot ulcers, venous stasis ulcers, pressure ulcers, or ulcersand lacerations of any type that require advanced wound management. Thepurpose of these materials is to provide a moist environment to coverand protect the exposed tissue, and sometimes to stimulate optimalhealing as taught in U.S. Pat. Nos. 4,963,489, 5,266,480, and 5,443,950.All patents listed in the preceding paragraph are herein incorporated byreference in their entirety.

The composition may be used as an adhesion barrier in general,gynecologic, and ENT surgical applications to reduce the incidence,extent, and severity of post-operative adhesions. Adhesions are a typeof scar tissue that forms a connection between two organs or surfacesthat are normally separate in the body. It is hypothesized that the freeblood and plasma that result from surgery can form fibrin strandsbetween tissues acutely; these strands can mature within a time span ofdays into permanent tissue bands which can interfere with normal organfunction and lead to other serious clinical complications. They aresometimes associated with endometriosis and pelvic inflammatory diseaseand are known to frequently form after abdominal, pelvic, or sinussurgery as taught in U.S. Pat. Nos. 5,852,024, 6,551,610, and 5,652,347.Over 90% of patients that undergo surgical procedures of this type mayform adhesions. The composition may be formed such that a lumen ismaintained in the body of the composition to enable ongoing airflow(i.e. during application following sinus surgery) or drainage of fluids.The composition may also be used as a stent to maintain separationbetween tissues. In another example, the composition may be used as anethmoid spacer to maintain an opening into the ethmoid sinuses followingsurgery. All patents listed in the preceding paragraph are hereinincorporated by reference in their entirety.

The compositions described herein may be used as a surface coating onmedical devices or tissues to prevent the formation of biofilm, andbacterial or fungal colonies. The selection of a strongly cationicpolysaccharide (e.g. Chitosan) as a component of the hydrogel networkallows for a continuous surface coating on implants and disposablemedical devices that provides a hindrance to biofilm deposition(Carlson, R. P. et. al., Anti-biofilm properties of chitosan coatedsurfaces. Journal of Polymer Science, Polymer Edition, 19(8):pp1035-1046, 2008). The mechanism of action may be twofold, the physicalstructure of the polysaccharide may function disrupt the bacterial cellwall or the cationic nature of the polysaccharide may be exploited tobind with anionic antibiotic agents. Alternatively, a non-polysaccharidecomponent or additive may be used to provide similar antimicrobial,antibacterial, or antifungal properties (e.g., silver). An importantapplication of a surface coated that provides infection control is inthe prevention or treatment of osteomyelitis. Osteomyelitis is aninfection of bone or bone marrow with a propensity for progression dueto pyrogenic bacteria. The presentation of osteomyelitis can be observeddue to iatrogenic causes such as joint replacements, internal fixationof fractures, or root canalled teeth. The hydrogel composition of thisinvention could allow for localized sustained antibiotic therapy.Furthermore, the composition may be designed to prevent or mitigatebacterial or fungal infections, reducing or eliminating the need forprolonged systemic antibiotic therapy as taught in U.S. Pat. Nos.5,250,020, 5,618,622, 5,609,629, and 5,690,955. All patents listed inthe preceding paragraph are herein incorporated by reference in theirentirety.

The compositions described herein can be used effectively to form porousand non-porous scaffolds of controlled microstructure favorable to cellseeding and tissue engineering applications. Methods of control of poresize and structure include the following: freeze drying(lyophilization), salt extraction, the use of foaming agents suchhydrogen peroxide, and other methods well known in the art. Multiplecell lines are of contemporary interest to enable the growth and repairof complex tissues using these porous and non-porous scaffolds such asvasculature, epithelial tissue, Islet cells for the formation of atissue engineered pancreas, nerve regeneration, cartilage regenerationand repair, bone growth and repair, and connective and soft tissuerepair (ventral and inguinal hernia, pelvic floor reconstruction,vaginal slings, rotator cuffs, tendon, etc.).

The hydrogel composition of this invention may be used in the controlleddelivery or administration of therapeutic or palliative agents. Thecomposition may include a synthetic component that acts as a carrier ordepot for the therapeutic or palliative agent. The agent may becovalently bound to the structure of the hydrogel matrix or physicallyentrapped within the hydrogel matrix. The rate of release of thetherapeutic or palliative agents may be controlled by modifying thecomposition of the invention. Targets of contemporary interest includethe following: paclitaxel for the treatment of tumors, insulin for thetreatment of diabetes, analgesics or anesthetics for the treatment ofpain, vasoconstrictors for the control of blood pressure such asamphetamines, antihistamines, pseudo-ephedrine, and caffeine,vasodilators for the control of blood pressure such as alpha blockers,nitric oxide inducers, and papavarine, cholesterol lowering drugs suchas statins (e.g. lovostatin), procoagulants for the control of clottingsuch as protamine sulfate, thrombin, fibrin, and collagen,anticoagulants for the control of clotting such as heparin, coumadin,glycoprotein 2-β-3-α, warfarin, abciximab, and clopidogrel bisulfate,and selective serotonin reuptake inhibitors such as fluoxetine toprovide palliative treatment of depression, obsessive/compulsivedisorders, bulimia, anorexia, panic disorders, and premenstrualdysphoric disorders, and mono amine oxidase inhibitors such asphenelzine for the palliative treatment of depression. The hydrogelcompositions may be used as a carrier for synthetic and human-based boneregrowth agents such as recombinant human bone morphogenic protein aswell as biomimetic materials usable for this indication such as B2A,F2A, PBA, LA1, VA5, PBA, LA1, VA5, B7A, F9A, F5A, and F20A fromBioSurfaces Engineering Technology, heterodimeric chain syntheticheparin-binding growth factor analogs as taught in U.S. Pat. No.7,528,105, positive modulator of bone morphogenic protein-2 as taught inU.S. Pat. Nos. 7,482,427 and 7,414,028, growth factor analogs as taughtin U.S. Pat. No. 7,414,028, and synthetic heparin-binding growth factoranalogs as taught in U.S. Pat. No. 7,166,574, all incorporated herein byreference in their entirety.

The compositions of the current invention have a variety of usesespecially in the area of cosmetic surgery and dermatology. Malleable,flowable compositions may be prepared as injectable formulations, andare suitable for superficial to deep dermal augmentation, for example tocorrect, fill, and support dermal wrinkles, creases, and folds as wellas lips as taught in U.S. Pat. Nos. 5,827,937, 5,278,201 and 5,278,204.Larger volume injections can be envisioned for augmentation of breast,penile glans, and other anatomic positions in the body as taught in U.S.Pat. No. 6,418,934; all listed patents are incorporated herein byreference in their entirety. Body sculpting procedures, including breastaugmentation, are contemplated for cosmetic and reconstructive purposes.Augmentation of the glans of the penis is used for treatment ofpremature ejaculation. Historically, the main limitation of medicaltreatment for premature ejaculation is recurrence after withdrawal ofmedication. Glans penis augmentation using injectable compositions ofthe invention facilitate treatment of premature ejaculation via blockingaccessibility of tactile stimuli to nerve receptors. The compositions ofthe invention could also be used as an injectable bulking agent forsphincter augmentation to control incontinence. In this application, thematerial is injected directly into the sphincter tissue to improve andaugment the tissue structure such that sphincter control could berestored. The compositions of the invention may also be used as a fillerfor breast implants, and as a filler for resorbable implants such asthose used for placement against bone and for filling of voids such asbetween bones as taught in US. Published Pat. App. 2006/0241777 andherein incorporated by reference in their entirety.

The composition described herein may be used as a space filling agentand energy barrier to attenuate existing energy-based procedures andreduce current dose limiting morbidity issues in adjacent tissue. Thehydrogel composition of this invention acts as a transient bufferbetween the non-diseased tissue and the tumor target. The benefits ofthis approach are twofold; the space filling attribute of theformulation physically moves the collateral tissue away from the targettumor towards which the energy is applied, furthermore, the compositionmay be formulated to include additives that attenuate the strength ofthe applied radiation or other energy. For example, the composition maybe used to reduce radiation damage of the prostate duringradiotherapeutic procedures. The displacement of the tumor away fromhealthy tissue described herein is also applicable to head and neckcancer, pelvic, thoracic, breast and soft tissue sarcomas. A further useof this composition in radiotherapy and surgical tumor removalprocedures is using the composition as a marking system to delineate theboundary of the tumor.

The compositions of the current invention may be used to fill voids intissue. Potential uses include the treatment of voids in bone, bothweight bearing and non-weight bearing, the treatment of voids or gaps inarticular cartilage, voids caused by a biopsy procedure, and septaldefects of the heart. The treatment of these voids can be enhanced bythe inclusion of biologically active agents and biologically activatingagents in the hydrogel formulation. For example, recombinant human bonemorphogenic protein or allograft human derived bone materials, ordemineralized bone matrices, or synthetic biomimetic materials may beincorporated into the composition to aid in the treatment of bone voids.

The compositions of the current environment can be may be used as asynthetic synovial fluid or other type of lubricating agent. Byincorporating synthetic polymers that are highly hydrophilic, thesematerials may find application in fields such as tendon or ligamentrepair and thoracic surgery. The adhesion of a lacerated tendon that hasundergone surgical repair to the tendon sheath reduces the range ofmotion of the affected digit or limb and increases the work required toattain the range of motion that remains. The deposition of a flowableslurry of the hydrogel composition between the surgically repairedtendon and the tendon sheath may act to reduce friction and enable alower work of extension for the affected tendon. In thoracic surgery,adhesions may form after thoracic interventions. The introduction of ahydrogel described herein may prevent or reduce the formation ofadhesions between the pleura, and in addition, provides a lubricant tomovement of the adjacent tissue past each other.

Kits

Also provided are kits for use in practicing the subject methods, wherethe kits typically include a hydrogel formulation that has been curedprior to shipment to the user. Containers are understood to refer to anystructure that may hold or surround the components of the hydrogelcomposition of the invention; exemplary containers include syringes,vials, pouches, capsules, carpules, ampules, cartridges, and the like.The containers may be shielded from visible, ultraviolet, or infraredradiation through the use of additional components (e.g. a foil pouchsurrounding a syringe) or through selection of the material propertiesof the container itself (e.g. an amber glass vial or opaque syringe).

The subject kits may also include a delivery device (which may or maynot include a mixing element), such as a catheter devices (e.g. tubeswith one or more lumens of identical or differing sizes and shapes withexit points of varying geometries, dimensions, and positions),syringe(s) of similar or different diameters and volumes, sprayelements, check valves, stopcocks, Y-connectors, air bleeder elements(e.g. a membrane that permits the removal of air from a liquid solutionprior to delivery to the patient), inlet ports or chambers for theintroduction of a forced air stream, disposable cartridges that allowfor prolonged deposition of the hydrogel composition, applicators orspreaders, assemblies for realizing a mechanical advantage in deliveringthe composition of the invention, housings or casings to protect andcontain the above mentioned components, and the like.

The kit may further include other components, e.g., desiccants or othermeans of maintaining control over water content in the kit, oxygenscrubbers or other means of maintaining control over oxygen contentwithin the kit, an inert gas atmosphere (e.g. nitrogen or argon),indicators to convey the maximum temperature experienced by the kit,indicators to convey exposure to sterilizing radiation, ethylene oxide,autoclave conditions, and the like, retaining or positioning structuresto prevent damage to the components (e.g. trays or packaging card), thatare required to maintain the product in good condition during transportand storage. The following examples are non-limiting and are meant todemonstrate the potential for kitting the hydrogel formulation.

In one embodiment, a container is supplied housing the cured, dried, andfragmented hydrogel formulation. A syringe is supplied containing abuffer appropriate for rehydrating the powder. The syringe is connectedto the fragmented hydrogel container and the buffer is introduced to thecontainer to rehydrate the fragmented hydrogel. The rehydrated hydrogelformulation is withdrawn into the syringe, at which point the user canconnect it to any of the exemplary device elements previously listed.

In a second embodiment, both the cured, dried, and fragmented hydrogelformulation and the appropriate buffer solution are supplied in a dualchamber syringe. The user rehydrates the dry hydrogel fragments bydepressing the syringe plunger and combining the buffer solution withthe dry hydrogel fragments. The user can then connect the syringe to anyof the exemplary device elements previously listed.

In a third embodiment, the cured, dried and fragmented hydrogelformulation is supplied in a syringe in the rehydrated state. The usercan connect the syringe to any of the exemplary device elements thathave been previously listed.

In fourth embodiment, the cured, dried and fragmented hydrogelformulation is supplied in a pouch or container for direct applicationto the target site.

In addition to above-mentioned components, the subject kits typicallyfurther include instructions for using the components of the kit topractice the subject methods. The instructions for practicing thesubject methods are generally recorded on a suitable recording medium.For example, the instructions may be printed on a substrate, such aspaper or plastic, etc. As such, the instructions may be present in thekits as a package insert, in the labeling of the container of the kit orcomponents thereof (i.e., associated with the packaging or subpackaging)etc. In other embodiments, the instructions are present as an electronicstorage data file present on a suitable computer readable storagemedium, e.g. CD-ROM, diskette, etc. In yet other embodiments, the actualinstructions are not present in the kit, but means for obtaining theinstructions from a remote source, e.g. via the internet, are provided.An example of this embodiment is a kit that includes a web address wherethe instructions can be viewed and/or from which the instructions can bedownloaded. As with the instructions, this means for obtaining theinstructions is recorded on a suitable substrate.

EXAMPLES

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use the present invention, and are not intended to limit thescope of what the inventors regard as their invention nor are theyintended to represent that the experiments below are all or the onlyexperiments performed. Efforts have been made to ensure accuracy withrespect to numbers used (e.g. amounts, temperature, etc.) but someexperimental errors and deviations should be accounted for. Unlessindicated otherwise, parts are parts by weight, molecular weight isweight average molecular weight, temperature is in degrees Centigrade,and pressure is at or near atmospheric.

Example 1

A multi-armed polyethylene glycol with amine active groups was combinedwith chitosan at a 10:1 ratio of polyethylene glycol to chitosan insodium borate buffer. An equal volume of a multi-armed polyethyleneglycol with ester active groups reconstituted in sodium borate buffer ata 2:1 ratio of polyethylene glycol ester to polyethylene glycol aminewas mixed with the chitosan solution. After one hour had passed, a firm,clear hydrogel had formed (FIG. 4).

Example 2

The sample of example 1 was dried under ambient temperature and pressureuntil the water content of the hydrogel had reached equilibrium with theenvironment (as determined by mass measurement). The sample wassubsequently fragmented utilizing a freezer/mill to achieve a finelymilled powder (FIG. 5).

Example 3

The dry powder of example 2 was then rehydrated in a saline solutioncontaining a blue-violet dye for purposes of visualization to obtain aslurry of cured, hydrated particles. The slurry was sufficientlyflowable to allow extrusion through an 18G needle with minimal pressure.

Example 4

A multi-armed polyethylene glycol with amine active groups was combinedwith chitosan at a 4:1 ratio of polyethylene glycol to chitosan insodium borate buffer. An equal volume of a multi-armed polyethyleneglycol with ester active groups reconstituted in sodium borate buffer ata 2:1 ratio of polyethylene glycol ester to polyethylene glycol aminewas mixed with the chitosan solution. After one hour had passed, a firm,clear hydrogel had formed. This sample was sectioned into pieces andloaded into a syringe. A female-female luer connector and a secondsyringe were connected to the initial syringe to enable syringe tosyringe mixing (FIG. 6). A total of 10 passes were performed on thehydrogel formulation, resulting in a slurry that was able to be extrudedfrom an 18G needle (FIG. 7).

The preceding merely illustrates the principles of the invention. Itwill be appreciated that those skilled in the art will be able to devisevarious arrangements which, although not explicitly described or shownherein, embody the principles of the invention and are included withinits spirit and scope. Furthermore, all examples and conditional languagerecited herein are principally intended to aid the reader inunderstanding the principles of the invention and the conceptscontributed by the inventors to furthering the art, and are to beconstrued as being without limitation to such specifically recitedexamples and conditions. Moreover, all statements herein recitingprinciples, aspects, and embodiments of the invention as well asspecific examples thereof, are intended to encompass both structural andfunctional equivalents thereof. Additionally, it is intended that suchequivalents include both currently known equivalents and equivalentsdeveloped in the future, i.e., any elements developed that perform thesame function, regardless of structure. The scope of the presentinvention, therefore, is not intended to be limited to the exemplaryembodiments shown and described herein. Rather, the scope and spirit ofpresent invention is embodied by the appended claims.

That which is claimed is:
 1. A composition comprising a plurality ofhydrogel fragments, wherein each hydrogel fragment in the compositioncomprises: a biologically active agent; and a hydrogel comprising anacetylated polysaccharide, a multifunctional, multi-armed polyethyleneglycol polymer and a multifunctional, multi-armed crosslinker ofpolyethylene glycol, wherein: the acetylated polysaccharide orderivative thereof has a molecular weight of 1000 Dalton to 80,300Dalton, a degree of deacetylation of 70% to 99%, and at least twonucleophilic groups and is directly covalently bonded to themultifunctional, multi-armed polyethylene glycol polymer and directlycovalently bonded to the multifunctional, multi-armed crosslinker ofpolyethylene glycol; the multifunctional, multi-armed polyethyleneglycol polymer has a molecular weight of 5,000 Dalton to 30,000 Dalton,and comprises at least two nucleophilic groups and is directlycovalently bonded to the acetylated polysaccharide or derivative thereofand is directly covalently bonded to the multifunctional, multi-armedcrosslinker of polyethylene glycol; and the multifunctional, multi-armedcrosslinker of polyethylene glycol has a molecular weight of 5,000Dalton to 30,000 Dalton, and comprises at least two electrophilic groupsand is directly covalently bonded to the acetylated polysaccharide orderivative thereof and is directly covalently bonded to themultifunctional, multi-armed polyethylene glycol polymer, wherein theacetylated polysaccharide or derivative thereof does not act as across-linking agent in the hydrogel.
 2. The composition of claim 1,wherein the hydrogel fragments are a dry powder.
 3. The composition ofclaim 1, wherein the hydrogel fragments are lyophilized.
 4. Thecomposition of claim 1, wherein the hydrogel fragments are milledfragments.
 5. The composition of claim 1, wherein the hydrogel fragmentsare pulverized fragments.
 6. The composition of claim 1, wherein thehydrogel fragments are crushed fragments.
 7. The composition of claim 1,wherein the hydrogel fragments are grinded fragments.
 8. The compositionof claim 1, wherein the biologically active agent is a steroid.
 9. Thecomposition of claim 8, wherein the steroid is mometasone furoate ortriamcinolone.
 10. The composition of claim 1, wherein the biologicallyactive agent is an antibiotic.
 11. The composition of claim 10, whereinthe antibiotic is gentamicin.
 12. The composition of claim 1, whereinthe biologically active agent is a plasma protein, an enzyme, anantiseptic agent, an antineoplastic agent, an antifungal agent, anantiviral agent, an anti-inflammatory agent, a growth factor, ananesthetic, a cell suspension, a cytotoxin, a cell proliferationinhibitor, a biomimetic, an analgesic, a chemotherapeutic, avasoconstrictor, a vasodilator, a cholesterol-lowering agent, aprocoagulant, a selective serotonin reuptake inhibitor, a bonemorphogenic protein, a growth factor, or a growth factor analog.
 13. Thecomposition of claim 1, wherein the polysaccharide or derivative thereofis a chitin, chitosan, or derivative thereof.
 14. The composition ofclaim 1, wherein the polysaccharide or derivative thereof is soluble inan aqueous solution.
 15. The composition of claim 14, wherein theaqueous solution is alkaline and the polysaccharide or derivativethereof is soluble in the aqueous solution up to a concentration of 30mM.
 16. The composition of claim 1, further comprising one or more of athickening agent, a foaming agent, a visualization agent, or aradiopaque agent.
 17. The composition of claim 1, wherein themultifunctional, multi-armed polyethylene glycol polymer comprises estergroups to provide for degradation via hydrolysis.
 18. The composition ofclaim 1, wherein the ratio of multifunctional, multi-armed polyethyleneglycol polymer to polysaccharide or derivative thereof is from 5:1 to10:1 by mass.
 19. A kit, comprising: the composition comprising theplurality of hydrogel fragments of claim 1, and a delivery device toprovide for delivery of the hydrogel fragments to a target area ortissue.
 20. The kit of claim 19, wherein the composition comprising theplurality of hydrogel fragments is provided in a first container and abuffer solution is provided in a second container.
 21. The kit of claim20, wherein the container for the composition comprising the pluralityof hydrogel fragments comprises a first syringe and the container forthe buffer solution comprises a second syringe.
 22. The kit of claim 20,wherein the container for the composition comprising the plurality ofhydrogel fragments comprises a pouch and the container for the buffersolution comprises a syringe.
 23. The kit of claim 20, wherein thecomposition comprising the plurality of hydrogel fragments and a buffersolution are provided within a single syringe.
 24. The kit of claim 23,wherein the syringe is a dual chamber syringe, and wherein thecomposition comprising the plurality of hydrogel fragments is providedin a first chamber of the syringe and the buffer solution is provided ina second chamber of the syringe.
 25. The kit of claim 19, wherein thecomposition comprising the plurality of hydrogel fragments is providedas a dry particulate in a container.
 26. The kit of claim 19, whereinthe composition comprising the plurality of hydrogel fragments isprovided as a semi- or fully hydrated particulate in a container.